There is a lot of discussion on the scale websites as to the correct colors for the streaky green. Even if it should be green or brown. I am going with a brownish olive for the base then will experiment with dry brushing a greener olive a dark gray and perhaps a black until I am happy.

The nice thing about using Solartex (natural) and electric power is I will airbrush using latex paint from Home Depot thinned with Floetrol. And as Home Depot will make up 8 oz paint color samples for less then $3.00 it is inexpensive to experiment.

Thanks Brad! The Pfalz I'm considering building should weigh around 10-11 lbs, and has a 74 inch wing span. How big a power system do you think I need? Is moto calc free, if so where can I download it from?

Depending on weather you trust MotoCalc or Scorpion Calc it should (WOT) draw ~60a and produce about ~200 oz thrust and a pitch speed of ~40 mph.

Brad

Servo Bus? Is that battery going to power the servos direct then signal wires only to the receiver? I've often wondered about doing that but had not heard of it being done before. What are all of the benefits? Thanks

Servo Bus? Is that battery going to power the servos direct then signal wires only to the receiver? I've often wondered about doing that but had not heard of it being done before. What are all of the benefits? Thanks

Dave

Dave it is a feature of the new Hitec Optima 2.4G receivers to separately power the radio side of the RC from the servo bus. There is a SPC port that can accept up to 36v for the radio side and if you use it, then any battery connected to the regular battery port just powers the servos. That way it would be impossible for the servos to pull the voltage so low that the RX to brownout.

There is a lot of discussion on the scale websites as to the correct colors for the streaky green. Even if it should be green or brown. I am going with a brownish olive for the base then will experiment with dry brushing a greener olive a dark gray and perhaps a black until I am happy.

The nice thing about using Solartex (natural) and electric power is I will airbrush using latex paint from Home Depot thinned with Floetrol. And as Home Depot will make up 8 oz paint color samples for less then $3.00 it is inexpensive to experiment.

Brad

Brad
Have you started the paint job yet? Normally the first coat or two on Dacron is thinned Nitrate dope. It will really bond to the Dacron and give a good start for the latex. Hope I'm not too late.
Dave

Haven't started yet, I built a spray box over the weekend. When I ordered the Solartex (natural) I checked with Dave Lewis at Balsa USA and his advise was no primer just go with thinned latex..... but now I am wondering.

Depending on weather you trust MotoCalc or Scorpion Calc it should (WOT) draw ~60a and produce about ~200 oz thrust and a pitch speed of ~40 mph.

Brad

If you've run this through motocalc, they suggest this motor is going to run very hot, over 400 degrees with that 20X8 prop. That puts you at risk of a burned up motor during flight, and dead stick landings. That 20X8 prop is more of a match for my Hacker A60-16M motor, a unit that is rated for 2400 watts. I'm running a 19X12 prop on this motor, it pulls 70 Amps on 12S2P A123 cells. And, per motocalc, efficiency is 91%. And predicted thrust is some 350 ounces. (I've got a Harbor freight 40 pound pull scale on order to check this!)

I've got a similar sized Hacker A50-16S that runs with a 6S2P A123 pack and a 16X12 APC-E prop. This is a nice combination. Other club members have run this same motor with a 6S Lipo with a smaller 15 inch diameter propeller. And, putting a 20x8 prop on this expensive motor would also likely burn it up.

What is the over all weight of your model? If its much over 10-12 pounds or so, you might need a higher powered motor. IMHO, any motor that is running over perhaps 100 watts per ounce of motor weight is pushing it a little.

If you put in a range of propellers in motocalc, like 16X6 to 20X10, this program spits out a number of different results. You can click on each of them and get opinions and so forth. Some of the Scorpion results had motor efficiencies down less 70% or so. Motocalc suggests that a 16X8 prop would get you about 90% efficiency with about 150 ounces of thrust, and a pitch speed of 50 MPH. This is getting pretty important when dealing with kilowatt sized motors. IMHO, best to use propellers that allow efficiency to be in the mid 80% or higher at full power.

I checked it out last December with Lucien the resident Scorpion Motor guy and he responded that:

Brad,

The S-4025-16 motor would be a good choice for a big DR1 like that. With a 20x8 prop, you should pull around 60 amps at full throttle, and get about 13 pounds of thrust at 6000 RPM. You will have a pitch speed of 45 MPH at full throttle. The plane will fly very nicely at about 1/3 to 1/2 throttle pulling 20-25 amps. At that rate, you could get 20-25 minute flights from a 10,000mah battery pack.

I checked it out last December with Lucien the resident Scorpion Motor guy and he responded that:

Brad

OK

Be very careful with motor power settings on that 20 inch prop. That size propeller is more for a 2400 watt motor, than one that's rated at 1000 watts. And that Scorpion motor has a 6 mm shaft (0.235 inches). If the 20 inch prop ever hits the ground on a nose over, you've got a chance of bending the motor shaft.

Hackers are of course very good motors..... over the years I have used Hackers, Kontronics, Pleitenbergs and AXI's but found the Scorpions to perform just as well and provide equivalent quality for less then half the price.
If I bend a shaft it is easily replaceable so that is not a major concern.

Hackers are of course very good motors..... over the years I have used Hackers, Kontronics, Pleitenbergs and AXI's but found the Scorpions to perform just as well and provide equivalent quality for less then half the price.
If I bend a shaft it is easily replaceable so that is not a major concern.

Brad

General maximum rule of thumb for maximum power out of our brushless motors is about 100 watts per ounce of motor weight. This one is 2000/12.45, or 160 watts per ounce. And power lost in the windings alone at 75 amps is 75X75X0.034 or 191 watts.